What about something along the lines of having fish in every "level" of the tank? Such as having fish that stay toward the top(angels, ect.), fish in the mid-level(tetras and others), and bottom dwellers(cories, loaches).

Or what about a "Peek-a-Boo" theme? It would include fish peeking out from their caves, a forest of plant, or other favorite hiding place. I think that that would call for some unique photos.

One of These Things is Not Like the Others... is the theme I have thought of. It would include pics with one fish schooling with a shoal of others. An example would be a betta schooling with cories. I do realize that something like this has been done, but it was just two different fish getting along. Not one fish with a whole group of others.

My Fish and Me: This theme would have pics of the fish owners and their fish, of course. But, you couldn't just take a pic of yourself standing next to the tank. You'd have to artisticly include yourself in the pic to get a sort of elegent photo. Or you'd have to take a pic of your fish interacting with you in some way.

Not sure if this has already been said or done, but how about "Couples Only!". Pictures showing off couples of fish we breed, are trying to breed, or even strange couples that never leave eachothers sides.

And off of that comes the idea of "Best Friends". Showing pictures of different fish swimming together who you know to barely ever leave eachothers sides._________________